Background/Aims: The aim of the present study was to assess the influence of chronic angiotensin-converting enzyme (ACE) inhibitor administration on the development of contrast-induced nephropathy (CIN) in patients undergoing coronary angiography. Methods: A total of 230 patients with renal insufficiency and age ≧65 years were divided into two groups according to prior use of ACE inhibitors (ACE inhibitor group, n = 109; control group, n = 121). CIN was defined as an increase of ≧25% in creatinine over the baseline value within 48 h of angiography. Results: CIN occurred in 17 patients (15.6%) in the ACE inhibitor group and 7 patients (5.8%) in the control group (p = 0.015). Serum creatinine level increased from 1.34 ± 0.20 to 1.53 ± 0.27 mg/dl in the ACE inhibitor group and from 1.33 ± 0.18 to 1.45 ± 0.19 mg/dl in the control group (p < 0.001). Chronic ACE inhibitor administration was a risk indicator of CIN [odds ratio 3.37; 95% confidence interval 1.14–9.94; p = 0.028]. Multi-vessel coronary involvement (p = 0.001), hypoalbuminemia (p = 0.005), diabetes mellitus (p = 0.006), GFR ≤40 ml/min (p = 0.010), and congestive heart failure (p = 0.024) were other risk indicators of CIN. Conclusion: Chronic ACE inhibitor administration is a risk for developing CIN in elderly patients with renal insufficiency.